Residual strains in HY100 polycrystals: Comparisons of experiments and simulations

Residual stresses commonly arise in metallic components following plastic d eformation and can have a significant effect on the mechanical properties. At the scale of the crystals, stresses are directly related to changes in l attice spacing. Neutron diffraction provides an effective method of measuri ng the spacing of atomic planes in crystal lattices with sufficient precisi on to determine the elastic (lattice) strains. In this work, tensile specim ens were loaded and unloaded in situ to progressively larger amounts of pla stic strain. Neutron diffraction measurements were taken at various points in the loading history, and the data were reduced to give the average elast ic strains in subsets of the crystals characterized by common crystallograp hic directions. Using the finite element method, lattice strains were computed at the cryst al level by modeling a polycrystal grain by grain. Elastic strains were ext racted for sets of crystals corresponding to those sets examined by diffrac tion at comparable points in the loading history. Detailed comparisons for a steel (HY100) indicate that the model shows good agreement in predicting the lattice strains, both in the loaded and unloaded states. Further, the s imulations elucidate aspects of the distributions of lattice strains that a rise from the grain-to-grain interactions.